It is known to deploy active devices of a vehicle according to a certain detected threshold. Such active devices may comprise for example occupant restraints such as active seat belt tensioners, active seat bolsters or other resettable devices intended to enhance occupant comfort during driving.
The threshold may be determined by, for example, proximity to an obstacle, or in response to reaching a predetermined speed.
A vehicle occupant will tend to move in the vehicle seat under the effect of cornering forces, and ideally an active device should be deployed before such movement commences.
There may however be an inevitable delay in deployment of an active device as the measured parameter increases toward the threshold, and it would be desirable to provide compensation whereby this delay is eliminated or at least ameliorated in certain conditions of use of the vehicle.
In particular, the lateral acceleration of a vehicle typically peaks just prior to the vehicle exiting a corner, thus causing an inherent delay in actuation or deployment of an active device of the vehicle in response to high cornering forces, where the device is triggered at a threshold. Lateral acceleration alone is thus an unsuitable indication as to the category of a cornering event, because the acceleration value peaks as the vehicle exits rather than enters a corner.
As a consequence the vehicle occupant is generally moving relative to the interior of the vehicle as the active device is deployed, and is typically arrested abruptly by a locked seat belt. This solution is thus not optimised for occupant comfort, and may be irritating if the threshold is set too low because the active device(s) will be repeatedly deployed. On the other hand a high threshold permits greater movement of an occupant before deployment, and a correspondingly higher contact load as the active device has effect.
What is required is an early indication of the category of a cornering event so that activation of such active devices can occur with sufficient time for the active device to deploy in a timely manner, and have a more acceptable effect on the vehicle and/or the vehicle occupants. By category is meant a measure of the increasing effect of a corner on the vehicle and occupants. Thus a large radius corner may have a low category, and a small radius corner may have a high category for a given vehicle speed. Ideally a solution should have a small number of measured variables, or inputs, so as to facilitate a rapid calculation/assessment of the need to trigger an active device of the vehicle.
It is an aim of the present invention to address this issue. Other aims and advantages of the invention will become apparent from the following description, claims and drawings.